Molecular dynamics study of nanogrinding of single-crystal silicon under dual-abrasive superposition

To elucidate how dual-abrasive superposition governs material removal and surface integrity during nanogrinding of initially rough single-crystal silicon, molecular dynamics simulations were performed at abrasive spacings of L = 2–10 nm. A sequential dual-abrasive model was used to characterize atomic displacement, grinding forces, thermal and stress responses, radial distribution functions, and subsurface structural evolution. The results show that abrasive spacing controls a transition from strongly coupled superposition to increasingly independent grinding. At L = 2–6 nm, the trailing abrasive reprocesses the preformed groove, suppressing chip accumulation, smoothing the machined surface, reducing tangential and normal forces, and limiting subsurface damage. At L = 8–10 nm, the superposition effect weakens and separate grinding tracks develop, accompanied by higher average temperature, stronger local stress concentration, increased high-coordination structures, and a thicker subsurface damage layer. The orthogonal force increases under stronger superposition because of enhanced lateral interference between abrasives. These findings reveal the spacing-dependent atomic mechanisms of surface reconstruction, local structural evolution, and subsurface damage, providing a mechanistic basis for controlling surface integrity in multi-abrasive nanogrinding.